A new algorithm for the determination of protolytic constants from spectrophotometric data in multiwavelength mode: Calculations of acidity constants of 4-(2-pyridylazo)resorcinol (PAR) in mixed nonaqueous-water solvents.

A new efficient, simple and versatile algorithm is presented for determination of the protolytic constants from spectrophotmetric data in multiwavelength mode based on the combining of hard and soft modeling. The algorithm was checked by determining the acidity constants of a triprotic acid from theoretical and real absorption-pH data. The real spectral data are obtained from photometric titration of different solutions of 4-(2-pyridylazo)resorcinol (PAR) by a standard base solution under an inert atmosphere. The algorithm starts the minimization process using an user supplied number of components and initial guesses of the unknown parameters and refined in a least squares manner. New algorithm is implemented in the new version of DATAN package (version 3.1). The validity of the obtained results was checked by some well known programs such as DATAN 2.1, SPECFIT/32, SQUAD, a modified version of difference spectra and a A-pH curve method. The comparison of the outputs of the DATAN 3.1 with the other programs reveals that there is a very good agreement between the obtained results and mentioned programs.

Mitogen activated protein kinase inhibition by PD98059 blocks nerve growth factor stimulated axonal outgrowth from adult mouse dorsal root ganglia in vitro.

Nerve growth factor stimulated axonal outgrowth from explanted mouse dorsal root ganglia is dependent on mitogen activated protein kinase. PD98059 ([2-(2'amino-3'-methoxyphenyl)-oxanaphthalen-4-one]) blocks mitogen activated protein kinase by inhibiting its immediate upstream activator, mitogen activated protein kinase kinase (also known as MEK). Here we used PD98059 to study the role of mitogen activated protein kinase in the axonal outgrowth of adult dorsal root ganglia explants. Whereas PD98059 at 50 microM left spontaneous axonal outgrowth unaffected, it markedly inhibited nerve growth factor stimulated axon growth when assessed after two days in culture. A mitogen activated protein kinase assay and immunoblotting using antibodies discriminating between activated and inactivated kinase, both confirmed that PD98059 reduced the amount of activated enzyme in nerve growth factor stimulated preparations, while the total amounts of the kinase remained unchanged. Immunohistochemistry revealed the presence of neuronal mitogen activated protein kinase kinase and mitogen activated protein kinase itself. The latter enzyme was found to be activated in the growing axons, as seen by whole-mount labelling. At the ganglionic level activated mitogen activated protein kinase was preferentially detected in satellite cells. The results show that nerve growth factor stimulated axonal outgrowth in vitro from adult mouse dorsal root ganglia utilizes the mitogen activated protein kinase pathway.